Attempts have been made to reduce or mask noise generated during a brake application through the application of sound coating on backing plates as disclosed in U.S. Pat. No. 3,998,301, the location of a screen member between the friction member and backing plate as disclosed in U.S. Pat. No. 4,154,322, the use of discrete friction members as disclosed in U.S. Pat. No. 4,315,563, selecting the shape of a friction pad whose engagement surface is less than the nodal diameter of a frequency that would create undesirable noise as disclosed in U.S. Pat. No. 4,705,146 and through modification of ingredients in the friction material. U.S. Pat. No. 5,456,339 discloses the use of modal analysis to identify points most sensitive to vibration and a method of reducing noise through the removal of selected portions of a brake friction pad to modify such sensitivity. While most of the methods and structure in the prior art to reduce noise will perform in an adequate manner most have not been widely accepted by the automobile industry primarily because of the added cost associate for such brake systems.
It is known that most structures vibrate and such vibration is often the result of dynamic forces applied to such structures. The vibration of the structures in frequency domain is a product of the structure response spectrum and the spectrum of the applied dynamic force, U.S. patent application Ser. No. 08/399,062 discloses a method of manufacturing a friction pad wherein a clamping force is varied to change the communication of frequency between members to attenuate noise during a brake application. U.S. Pat. No. 4,220,223 discloses a friction pad having a uniform chamfer along the leading and trailing edges of a friction pad to modify a dynamic force that can be introduced into a brake system on engagement of a friction pad with a caliper. While this structure may reduce dynamic loads under certain applications high frequency noise was observed during dynamometer test evaluation of a brake system which included a caliper, associated brake linings and a rotor. Modal analysis and/or frequency response analysis of such a brake system could be performed to determine the natural frequencies generated during a brake application and thereafter modify the structure in accordance with the teaching in the prior art to reduce noise however most customers do not want to incur any additional cost associated with such analysis.